SPEED SENSORLESS FIELD-ORINTED CONTROL OF INDUCTION MOTORS WITH AN IMPROVED FLUX ESTMATOR

This paper proposes a programmable low pass filter(LPF) to estimate stator flux for speed sensorless stator flux orientation control of induction motors. The programmable LPF is developed to solve the dc drift problem associated with a pure integrator and a LPF with fixed pole. The pole of the programmable LPF is located far from the origin to decrease the time constant as speed increases. The programmable LPF has the phase and the magnitude compensator to exactly estimate stator flux in a wide speed range. So, the drift problem is much improved and the stator flux is exactly estimated in the wide speed range.